The process of manufacturing leather from hides has changed relatively little for many years, and the many steps that comprise the process are well known in the industry. In general terms, there are preliminary steps to preserve the hides and prepare them for tanning, followed by the steps of tanning and further processing. A typical sequence of steps in the preliminary, pre-tanning part of the process is curing with salt (sodium chloride), soaking and washing, defleshing, liming, unhairing, bating and pickling.
The salt-curing of the hides, done as the first step, is carried out either by immersing the hides in a brine solution, by wet salting or by dry salting. The purpose of salt-curing is to retard spoilage prior to carrying out the remainder of the leather-making process. It is common in North America and many other parts of the world for hides to be preserved by salt-curing and then be shipped to overseas tanneries for the further processing and tanning.
Another common method of curing hides includes processing through the preliminary steps in the conventional manner and tanning with chromium sulphate, which results in a product termed wet blue, which is then further tanned, again, often at overseas tanneries. Even with this process, however, salt-curing may be done as a preliminary step.
The practice of salt-curing causes significant environmental damage. When the curing and the tanning are done at different facilities, this damage occurs in both places.